CMP Technological Paradigm Shift To Surface Cleaning. Hong Jin Kim Advanced Module Engineering, GLOBALFOUNDRIES

Transcription

1 CMP Technological Paradigm Shift To Surface Cleaning Hong Jin Kim Advanced Module Engineering, GLOBALFOUNDRIES

2 Presentation Focus On.. CMP-induced Defects: -. CMP Process -. Role and Effect of CMP in-situ Cleaning -. Brush Cleaning -. Examples of CMP-induced Defects and Their Removal Cleaning Perspective of CMP Process 2

3 CMP: Planarization Technology Planarization & Polishing Material Removal & Separation 3

4 CMP Equipment: Polisher and Cleaner Polisher Cleaner Megasonic Brush Scrubber Non-Contact Cleaning (ex. fluid jet) Polishing and cleaning are in-situ process: polishing cleaning at the same equipment 4

5 Historical CMP Technology Development 1927, Preston published glass polishing theory 1972, Raytheon, first practice CMP for planarization 1983, IBM first planarized Pbsilicate glass for STI 1983, IBM first planarized Pbsilicate glass for STI 1986, CMP developed in IBM, called FRED 1987, CMP development begin at IBM 1989, oxide/al/w CMP implemented 1991, IC pad born 1995, 1 st ph.d for CMP 1997, 1 st CMP textbook 2000, 300mm CMP setup in industry for manufacturing , CMP developed explosively in materials, consumables, tools and functions 2017, Core process in the semiconductor manufacturing Michael Fury, You want to do what to my wafer, Korea CMP User Group Meeting 2014 Gautam Banerjee and Robert L. Rhoades, Chemical Mechanical Planarization: Historical Review and Future Trend, ECS Transactions, 2008 Images from google 5

6 ITRS Roadmap Transistor Scaling: 1.Geometrical Scaling ( ~ 2003) 2.Equivalent Scaling ( ~ 2021) 3.Power Scaling ( ~ 203x) P. Gargini, SPCC2016 Practical scaling may end at 10nm? Or 7nm will be an end of scaling? Image from google 6

7 Post CMP in-situ Cleaning CMP: is known as the most defect generated process in semiconductor fabrication However, CMP is also highly favorable process condition for cleaning aspect cf. Challenges of wet cleaning (ex-situe): pattern damage, strong adhesion of small particle (at dry surface state) to wafer surface CMP (pros and cons as cleaning perspectives): In-situ process Flat surface: no pattern damage strong physical cleaning acceptable Single wafer process Wet process: weak adhesion between particle and wafer surface Sufficient material undercut No standard method to estimate particle removal efficiency Variation in incoming wafer surface and defect level is very high Limited cleaning chemical available for manufacturing (HF, SC-1, NH4OH )

8 Strategy for Post CMP In-situ Cleaning Wet Cleaning Strategy for the Next Generation Hyosan Lee, Next Generation Particle Cleaning, Semicon Korea 2015 Cleaner Clean chemical Dryer Brush, Brush..

9 Particle Removal vs Contamination Brush Contact Particle removal: drag force > adhesion force f (brush RPM, brush gap ): higher brush RPM high particle removal Wafer contaminated by brush cleaning more contact, more particle Ref.) Ahmed A. Busnaina, IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING, VOL. 15, NO. 4, NOVEMBER 2002, pp Ref.) H-J Kim et.al., MICROELECTRONIC ENGINEERING 136, 2015, PP

10 Brush Cleaning and Defect Signature Defect Signature by Brush Cleaning Brush Gap Brush RPM Chem. Flow Physical Force Contact Behavior Friction Torque Porosity Post Brush Clean Defect??? Brush Cleaning is NOT ONLY clean the wafer BUT ALSO contaminate wafer PRE vs C.C. 10

11 Effect of Brush Recipe on Cross Contamination Low RPM longer contact duration high cross contamination Optimum RPM high PRE & optimum duration lowest cross contamination High RPM high contact frequency increase cross contamination Negative brush gap high down force increase contact area high cross contamination At 0 gap nodule non-uniformity high cross contamination/ low PRE 11

12 Effect of Brush Lifetime

13 Effect of Slurry Incoming Wafer Effect Polishing with Slurry A - Cleaner Polishing with Slurry B Cleaner CMP cleaner performance is sensitively influenced by slurry

14 Effect of Cleaner Contamination Tool Type Megasonic BB1 BB2 Dryer A B 1 st cleaner loaded defects more than following cleaner. Contamination depends on tool.

15 Chemical Mechanical Cleaning Effect of chemical buffing polishing on defects CMP CMC Buff CMP with cleaning chemical: Chemical Reaction + Physical Force to Wet Wafer Surface Effective cleaning process. No (Min.) material removal required (not matured process in industry yet)

16 Challenges and Opportunities Brush Cleaning Early brush defect Minimize cross contamination New design of brush and brush nodule Pre-broken brush Optimized brush properties, ex) porosity, pore size, softness Clean Chemical Almost same chemicals used for more than 15 years High performance of particle removal associated with brush cleaning No material damage with multi materials exposure Low cost, eco-friendly chemical (in particular, for Cu CMP) Cleaner Module Non-contact type cleaner module New design on cleaner module for advanced cleaning Monitoring for dryer

17 Summary Paradigm need to be shifted. Planarization /Polishing Cleaning CMP concept now encompasses cleaning in addition to traditional planarization concept. And role of cleaning becomes much more critical than previous device. CMP CMPC: Chemical Mechanical Polishing and Cleaning